Production process of titanium dioxide for plastic with high thermal stability

Abstract

The invention discloses a production process of titanium dioxide for plastics with high thermal stability, belongs to the technical field of titanium dioxide preparation, and aims to design titanium dioxide for plastics, which can improve the thermal stability as much as possible on the basis of maintaining good plastic matrix dispersity and lower water absorption. The temperature, the rotating speed and the pH value in the coating process are strictly controlled, and carbon dioxide is introduced in the coating process for auxiliary coating, so that aluminum ions in a sodium metaaluminate solution are promoted to uniformly nucleate on the surfaces of titanium dioxide particles, a uniform aluminum oxide protection layer is formed, the thermal stability of titanium dioxide is further improved, the water absorption is reduced, and the service life of the titanium dioxide is prolonged. The dispersity of titanium dioxide in polyolefin is obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium dioxide preparation, and in particular relates to a production process of titanium dioxide for plastics with high thermal stability. Background Art

[0002] Titanium dioxide coating is a treatment method that covers the surface of titanium dioxide with a thin film or coating. This coating usually improves the performance and application characteristics of titanium dioxide by forming a protective covering layer on the surface of titanium dioxide. The coating material can be various organic substances, such as sodium aluminate, silicone oil, silicone, etc. Titanium dioxide can be used in different fields, and titanium dioxide has different requirements for coating in different fields. When titanium dioxide is used in the field of coatings, it needs to provide covering power and glossiness. Titanium dioxide coating needs to have good weather resistance and chemical stability to ensure that the coating remains stable under different environmental conditions. Titanium dioxide When titanium dioxide is used in the plastic field, it is necessary to improve the appearance of the plastic product, improve weather resistance, reduce water absorption, and improve color stability; titanium dioxide is used in printing inks to provide whiteness and hiding power, and the titanium dioxide coating needs to have good dispersibility and stability to ensure that the ink pigment is evenly dispersed and maintains stability during the printing process; the existing titanium dioxide for plastics needs to have high thermal stability, good plastic matrix dispersibility and low water absorption. Therefore, it is necessary to design a titanium dioxide for plastics that can improve thermal stability as much as possible while maintaining good plastic matrix dispersibility and low water absorption. Summary of the invention

[0003] In response to the problems in the prior art, the present invention provides a preparation method and application of a phosphate-aluminum coating agent. By setting a series of reaction conditions, the aluminum ions in the sodium aluminate solution are promoted to uniformly nucleate on the surface of titanium dioxide particles to form a uniform aluminum oxide protective layer, thereby further improving the thermal stability of titanium dioxide, reducing water absorption, and significantly improving the dispersibility of titanium dioxide in polyolefins.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A production process of titanium dioxide for plastics with high thermal stability comprises the following steps:

[0006] Step 1: preparing a sodium aluminate solution;

[0007] Step 2: crush the titanium dioxide to 45 μm and the percentage of the sieve residue is ≤0.15%;

[0008] Step 3: adding the titanium dioxide obtained in step 2 into water, adding a dispersant and adjusting the pH value to 9-11 with caustic soda to obtain a slurry;

[0009] Step 4: Grind the slurry obtained in step 3 using a sand mill to disperse the titanium dioxide particles in preparation for subsequent coating;

[0010] Step 5: heating the slurry obtained in step 4 to t, adjusting the pH value of the system to pH 1, adding sodium aluminate as a coating agent for coating under stirring, after the addition of sodium aluminate, adjusting the pH value of the system to pH 2, maintaining the temperature at t, and the total coating time is 1 to 5 hours;

[0011] Step 6: After coating, the coated titanium dioxide obtained in step 5 needs to be aged, and the temperature is kept and stirred during the aging process;

[0012] Step 7: washing and filtering the titanium dioxide after the aging treatment in step 6 to remove excess coating agent and dispersant, and then drying;

[0013] Step 8: The titanium dioxide powder dried in step 7 is initially crushed, and then further ultra-finely crushed to obtain the final product.

[0014] Preferably, in step 1, the concentration range of the prepared sodium aluminate solution during the titanium dioxide coating process is 95 g / L to 105 g / L of aluminum oxide, and the molar ratio of sodium aluminate to titanium dioxide is 1:15.

[0015] Preferably, in step 3, the dispersant is one or more of sodium hexametaphosphate and sodium silicate.

[0016] Preferably, in step 5, t is 80-90°C.

[0017] Preferably, in step 5, the pH1 value is 10 to 10.5.

[0018] Preferably, in step 5, the pH2 value is 9 to 10.5.

[0019] Preferably, in step 5, during the coating process, carbon dioxide gas is introduced into the titanium dioxide suspension containing the coating agent, so that the coating agent slowly precipitates to form a film on the surface of the titanium dioxide particles.

[0020] Preferably, the flow rate of the introduced carbon dioxide is controlled at 20-600 ml / min.

[0021] Preferably, the stirring rate in step 5 is maintained at 200-400 r / min.

[0022] Preferably, in step 6, the aging temperature is maintained at 70-75° C., the stirring speed is 150 r / min, and the aging time is 60-90 min.

[0023] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0024] 1. When the pH value is 10-10.5, the aluminum film formed by sodium aluminate deposited on the surface of titanium dioxide has a higher thermal stability. This is because at this pH value, granular trihydroxy aluminum stone with clear interface and uneven size can be obtained, showing better thermal stability. At a higher pH value, the coating formed by sodium aluminate deposited on the surface of titanium dioxide has high thermal stability, and the film layer is continuous and dense, thereby achieving homogeneous nucleation.

[0025] 2. When the pH value is 10-10.5, the specific surface area of ​​the coated titanium dioxide increases from 6.73m 2 / g increased to 18.28m 2 / g, and the oil absorption value increased from 19.88g / mL to 32.46g / mL, which shows that when the pH value is 10-10.5, the coating treatment can increase the specific surface area and oil absorption value of titanium dioxide, and can significantly improve the dispersibility of titanium dioxide in plastics after coating.

[0026] 3. Using sodium aluminate to carry out inorganic surface treatment of titanium dioxide at a temperature of 80-90°C can make the particle size distribution of titanium dioxide after aluminum hydroxide coating more uniform and the Zeta potential changes from negative to positive. This change in potential helps to improve the dispersibility of titanium dioxide in the plastic matrix and promote the formation of homogeneous nucleation; the temperature of 80-90°C is conducive to the uniform coating of sodium aluminate on the surface of titanium dioxide, forming a continuous and dense coating layer, which effectively improves the thermal stability of titanium dioxide after coating.

[0027] 4. CO2 gas is introduced into an alkaline titanium dioxide suspension containing a coating agent to allow the coating agent to slowly precipitate and form a film on the surface of the TiO2 particles. The method of assisting the coating by introducing CO2 gas can make the film formation more uniform, which is conducive to homogeneous nucleation. By coordinating a series of measures in steps 1 to 5 of the present application, the coating process of titanium dioxide by sodium aluminate can be effectively controlled to achieve homogeneous nucleation. During the homogeneous nucleation process, the aluminum ions in the sodium aluminate solution are uniformly nucleated on the surface of the titanium dioxide particles to form a uniform alumina coating layer as much as possible, thereby reducing the agglomeration and sintering of the titanium dioxide particles at high temperatures. This uniform coating layer can improve the thermal stability of titanium dioxide. The uniform coating layer formed by homogeneous nucleation reduces the hydrophilic groups on the surface of titanium dioxide, and the uniform alumina layer can serve as a barrier to reduce the contact between moisture and the surface of titanium dioxide, thereby reducing its water absorption. The uniform alumina coating layer can reduce the interaction between titanium dioxide particles, so that homogeneous nucleation helps to improve the dispersibility of titanium dioxide in polyolefins. DETAILED DESCRIPTION

[0028] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application generally described and shown herein can be arranged and designed in various configurations. Therefore, the following detailed description of the embodiments of the present application provided in is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0029] Examples 1 to 5 and Comparative Examples 1 to 6

[0030] The values ​​of t, pH1 and pH2 are shown in Table 1

[0031] A production process of titanium dioxide for plastics with high thermal stability, characterized in that it comprises the following steps:

[0032] Step 1: preparing a sodium aluminate solution;

[0033] Step 2: crush the titanium dioxide to 45 μm and the percentage of the sieve residue is ≤0.15%;

[0034] Step 3: adding the titanium dioxide obtained in step 2 into water, adding a dispersant and adjusting the pH value to 10 with caustic soda to obtain a slurry;

[0035] Step 4: Grind the slurry obtained in step 3 using a sand mill to disperse the titanium dioxide particles in preparation for subsequent coating;

[0036] Step 5: The slurry obtained in step 4 is heated to t, the pH value of the system is adjusted to pH 1, and sodium aluminate is added as a coating agent under stirring to coat. After the sodium aluminate is added, the pH value of the system is adjusted to pH 2, the temperature is maintained at t, and the total coating time is 2.5h;

[0037] Step 6: After coating, the coated titanium dioxide obtained in step 5 needs to be aged, and the temperature is kept and stirred during the aging process;

[0038] Step 7: washing and filtering the titanium dioxide after the aging treatment in step 6 to remove excess coating agent and dispersant, and then drying;

[0039] Step 8: The titanium dioxide powder dried in step 7 is initially crushed, and then further ultra-finely crushed to obtain the final product.

[0040] In this embodiment, in step 1, the concentration range of the prepared sodium aluminate solution during the titanium dioxide coating process is 100 g / L of aluminum oxide, and the molar ratio of sodium aluminate to titanium dioxide is 1:15.

[0041] In this embodiment, in step 3, the dispersant is sodium hexametaphosphate.

[0042] In this embodiment, in step 5, t is 80-90°C.

[0043] In this embodiment, in step 5, the pH1 value is 10 to 10.5.

[0044] In this embodiment, in step 5, the pH2 value is 9 to 10.5.

[0045] In this embodiment, in step 5, during the coating process, carbon dioxide gas is introduced into the titanium dioxide suspension containing the coating agent, so that the coating agent slowly precipitates to form a film on the surface of the titanium dioxide particles.

[0046] In this embodiment, the flow rate of the introduced carbon dioxide is controlled at 20-600 ml / min.

[0047] In this embodiment, the stirring rate in step 5 is maintained at 360 r / min.

[0048] In this embodiment, in step 6, the aging temperature is maintained at 72° C., the stirring speed is 150 r / min, and the aging time is 75 min.

[0049] The Zeta potential of the coated titanium dioxide was tested by electrophoretic light scattering method, and the coated titanium dioxide sample was treated by vacuum. The specific operation steps were to put the sample into a vacuum container, evacuate the container to reduce the surface tension of water, make it easier for water to penetrate into the material, and then soak, weigh and calculate the water absorption rate. The specific test results are shown in Table 1.

[0050] Table 1: Selection of t, pH1 and pH2 values ​​and test table of thermal stability, plastic matrix dispersion and water absorption performance

[0051]

[0052]

[0053] Zeta potential is an important indicator for characterizing the stability of titanium dioxide colloid after coating. The higher the absolute value of Zeta potential, the more stable the system is, that is, the dissolution or dispersion can resist aggregation. A higher absolute value of Zeta potential usually means better thermal stability because the mutual repulsion between particles is enhanced, reducing the possibility of aggregation, thereby improving the stability of the material at high temperatures.

[0054] In plastic matrix composite materials, the change in Zeta potential is closely related to the dispersibility of titanium dioxide nanoparticles after coating; the increase in Zeta potential means that the repulsive force between nanoparticles is enhanced, thereby reducing aggregation and improving dispersibility. The larger the absolute value of Zeta potential, the better the dispersibility of nanoparticles in the polyethylene matrix and the better the performance of titanium dioxide after coating.

[0055] Through the above series of experiments, it can be seen that when t is 80-90°C, pH1 is 10-10.5, pH2 is 9-10.5 and the flow rate of carbon dioxide is 20-600ml / min, the thermal stability is high, the plastic matrix dispersion is best and the water absorption is low.

[0056] The above embodiments and comparative examples show that the present invention adopts the above reaction conditions to promote the uniform nucleation of aluminum ions in the sodium aluminate solution on the surface of titanium dioxide particles to form a uniform aluminum oxide protective layer, further improve the thermal stability of titanium dioxide, reduce water absorption, and significantly improve the dispersibility of titanium dioxide in polyolefins.

[0057] The above-mentioned embodiments only express the specific implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the protection scope of the present application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the technical solution concept of the present application, and these all belong to the protection scope of the present application.

Claims

1. A process for producing titanium dioxide for plastics with high thermal stability, characterized in that: The following steps are involved: Step 1: preparing a sodium aluminate solution; Step 2: crush the titanium dioxide to 45 μm and the percentage of the sieve residue is ≤0.15%; Step 3: adding the titanium dioxide obtained in step 2 into water, adding a dispersant and adjusting the pH value to 9-11 with caustic soda to obtain a slurry; Step 4: Grind the slurry obtained in step 3 using a sand mill to disperse the titanium dioxide particles in preparation for subsequent coating; Step 5: heating the slurry obtained in step 4 to t, adjusting the pH value of the system to pH 1, adding sodium aluminate as a coating agent for coating under stirring, after the addition of sodium aluminate, adjusting the pH value of the system to pH 2, maintaining the temperature at t, and the total coating time is 1 to 5 hours; Step 6: After coating, the coated titanium dioxide obtained in step 5 needs to be aged, and the temperature is kept and stirred during the aging process; Step 7: washing and filtering the titanium dioxide after the aging treatment in step 6 to remove excess coating agent and dispersant, and then drying; Step 8: The titanium dioxide powder dried in step 7 is initially crushed, and then further ultra-finely crushed to obtain the final product.

2. A process for producing titanium dioxide for plastics with high thermal stability according to claim 1, characterized in that: In step 1, the concentration range of the prepared sodium aluminate solution during the titanium dioxide coating process is 95 g / L to 105 g / L of aluminum oxide, and the molar ratio of sodium aluminate to titanium dioxide is 1:

15.

3. The process for producing titanium dioxide for plastics with high thermal stability according to claim 1, characterized in that: In step 3, the dispersant is one or more of sodium hexametaphosphate and sodium silicate.

4. The process for producing titanium dioxide for plastics with high thermal stability according to claim 1, characterized in that: In step 5, t is 80-90°C.

5. The process for producing titanium dioxide for plastics with high thermal stability according to claim 1, characterized in that: In step 5, the pH1 value is 10 to 10.

5.

6. The process for producing titanium dioxide for plastics with high thermal stability according to claim 1, characterized in that: In step 5, the pH2 value is 9 to 10.

5.

7. The process for producing titanium dioxide for plastics with high thermal stability according to claim 1, characterized in that: In step 5, during the coating process, carbon dioxide gas is introduced into the titanium dioxide suspension containing the coating agent, so that the coating agent slowly precipitates to form a film on the surface of the titanium dioxide particles.

8. The process for producing titanium dioxide for plastics with high thermal stability according to claim 7, characterized in that: The flow rate of the introduced carbon dioxide is controlled at 20-600 ml / min.

9. The process for producing titanium dioxide for plastics with high thermal stability according to claim 1, characterized in that: In step 5, the stirring rate is maintained at 200-400 r / min.

10. The process for producing titanium dioxide for plastics with high thermal stability according to claim 1, characterized in that: In step 6, the aging temperature is maintained at 70-75° C., the stirring speed is 150 r / min, and the aging time is 60-90 min.

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